JP2006084094A - Combustion device performing pilot combustion control - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce fuel consumption and heat radiation quantity by combustion of a pilot burner; and to reduce overshoot of a steam pressure. <P>SOLUTION: In the combustion device, it is controlled so that main combustion is stopped when the value is raised to a main combustion stop set value, and the main combustion is started when the value is lowered to a main combustion start set value based on a pressure or a temperature in a boiler, and pilot combustion can be controlled even after main combustion is stopped. A pilot stop determination set value which is a value between the main combustion stop set value and the main combustion start set value and pilot stop determination time are set, actual time (b) from attainment to the main combustion stop set value to the pilot stop determination set value is measured, and the executed pilot combustion is continued when the actual measured time (b) is shorter than the pilot stop determination time, and the executed pilot combustion is stopped when the value does not attain to the pilot stop determination set value even after the pilot stop determination time. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a combustion apparatus that has a main burner and a pilot burner and performs pilot combustion control that enables control to perform pilot combustion by the pilot burner even after the main combustion by the main burner is stopped.

  Combustion apparatuses having a large capacity main burner and a small capacity pilot burner are widely used. Combustion by the pilot burner includes a method in which the pilot burner is continuously burned while the combustion by the main burner is stopped, and a method in which the pilot burner also stops combustion when the combustion of the main burner is stopped. If the pilot burner continues to burn while the main burner is stopped, the main burner can be started in a short time because the pilot burner already has a flame when the main burner needs to be burned. It will be excellent. However, since fuel is also required for burning the pilot burner, there is a problem that if the time for burning only the pilot burner is long, there is a problem that the amount of fuel consumption increases, and air is used to burn the pilot burner. There is a problem in that heat dissipation increases if the feed continues. Conversely, when the combustion of the pilot burner is stopped while the main burner is stopped, the fuel consumption can be reduced compared with the case where the pilot burner is continuously burned, but the combustion start of the main burner is delayed. In particular, in the case of a combustion apparatus that needs to ventilate the combustion chamber before the start of combustion, since the combustion chamber ventilation time is required, the start of combustion is further delayed, which may cause a shortage of heat.

  Japanese Patent Application Laid-Open No. 2002-81605 describes that pilot combustion is stopped when main combustion does not start even if the pilot combustion is performed for the duration T in order to reduce the loss during the pilot combustion standby. Yes. This can prevent wasting fuel by continuing pilot combustion indefinitely. However, even in this case, fuel is wasted because pilot combustion is performed until the duration T ends. Further, when the duration T has elapsed, even if it is just before the main burner needs to be combusted, the pilot combustion is stopped, and therefore, the combustion preparation process may be started immediately after the end of the pilot combustion.

  In Japanese Patent Laid-Open No. 2002-81605, the duration T is increased / decreased based on the required load fluctuation, but it cannot be said to be sufficient for the above problem. Since the duration T is set based on the time from the main combustion stop to the next main combustion start, it cannot be set too short. For example, when it is determined that the load fluctuation is small, the duration T is set to 30 seconds as a short time. However, even in this case, pilot combustion for 30 seconds is necessary, and when main combustion is not required within 30 seconds, pilot combustion for 30 seconds becomes useless combustion. In addition, if a combustion request signal is issued immediately after the continuation time T has elapsed, the fuel up to that point is wasted due to the pilot combustion being stopped, and pre-purge is started from there. The start of main combustion will also be delayed. If the duration T is shortened, the pilot combustion is stopped more quickly. In this case, however, there is a high possibility that the pilot combustion is stopped before the main combustion is started even if the steam pressure decrease rate is fast. There is an increased risk of steam shortage.

  An example of a conventional time chart is shown in FIG. FIG. 5 shows that combustion of the main burner is stopped when the steam pressure value rises to the main combustion stop set value, and combustion of the main burner is started when the steam pressure value falls to the main combustion start set value. The pilot burner continues to burn for the duration T even after the main burner stops. If the steam pressure value drops to the main combustion start set value during the duration T, the pilot burner immediately burns the main burner. So that you can start. In FIG. 5, the main combustion is started, and the main combustion by the combustion of the main burner is continued until the steam pressure value reaches the main combustion stop set value. Then, the combustion of the main burner is stopped. At this time, the pilot burner continues to burn and performs pilot combustion for the duration T after the main combustion is stopped. Even if the combustion of the main burner is stopped when the steam pressure value reaches the main combustion stop set value, steam is generated due to residual heat, so an overshoot occurs in which the steam pressure value becomes higher than the main combustion stop set value. To do. Overshoot increases as the steam pressure rises faster.

The pilot combustion is performed for the duration T from the point K. If the steam pressure value falls to the main combustion stop set value during the duration T, the combustion of the main burner is started. However, in FIG. 5, the pilot combustion is stopped at the point L because the steam pressure value has not decreased to the main combustion stop set value at the point L at which the duration T has elapsed. Thereafter, since the steam pressure value has reached the main combustion start set value at the point M, the combustion preparation process such as pre-purge is performed from the point M. When starting main combustion from a state where combustion is stopped, a combustion preparatory step such as pre-purge is necessary, and during that time steam cannot be supplied, so the steam pressure value continues to decrease. When the combustion preparation process is completed, the pilot burner is then ignited and finally the main burner is started by starting the combustion of the main burner. In this case, the pilot combustion for the duration T is not useful at all, and only the heat is released by the consumption of fuel and the supply of combustion air. It will be good.
JP 2002-81605 A

  The problem to be solved by the present invention is that when it is necessary to restart the combustion of the main burner without delay, the combustion of the main burner can be immediately restarted. The purpose is to reduce the fuel consumption and heat release by combustion, and to reduce the overshoot of the steam pressure.

  The invention according to claim 1 performs control to stop main combustion by the main burner when it rises to the main combustion stop set value and to start main combustion when it falls to the main combustion start set value based on the pressure or temperature in the boiler. A combustion apparatus for a boiler that enables control to perform pilot combustion by a pilot burner even after the main combustion stop, for pilot stop determination that is a value between the main combustion stop set value and the main combustion start set value A pilot stop determination time determined based on the set value and the time required to change from the main combustion stop set value to the pilot stop determination set value is set, and the main combustion is stopped by reaching the main combustion stop set value. Measure the actual measurement time b from the time of stopping until the pressure or temperature drops to the pilot stop judgment set value. If the measured actual measurement time b is less than the preset pilot stop determination time, the pilot combustion is continued and the pilot stop is performed even if the preset pilot stop determination time has elapsed. When the set value for determination is not reached, control is performed to stop the pilot combustion that is being performed.

  According to the second aspect of the invention, based on the pressure or temperature in the boiler, the main combustion by the main burner is stopped when the main combustion stop set value is raised, and the main combustion is started when the main combustion start set value is lowered. A combustion apparatus for a boiler that enables pilot combustion by a pilot burner even after the main combustion is stopped, for pilot stop determination that is a value between the main combustion stop set value and the main combustion start set value The pilot stop determination time determined based on the set value and the time required for the change from the pilot stop determination set value to the main combustion stop set value is set. Measure the actual time a until the pressure or temperature rises to the main combustion stop set value after reaching If the measured time a is less than the preset pilot stop determination time, the pilot combustion is stopped and the main combustion stop set value is set even if the set pilot stop determination time elapses. When it does not reach, it is characterized in that control for performing pilot combustion is performed.

  According to a third aspect of the present invention, in the combustion apparatus that performs the pilot combustion control, when the main combustion is started, the combustion of the pilot burner is stopped, and when the main combustion is shifted to the pilot combustion, the main combustion stop set value is set. When the combustion transition set value that is between the main combustion start value and the main combustion start set value is reached, control is performed to start combustion by the pilot burner by overlapping with the main combustion, and the combustion transition set value is determined as the pilot stop determination. It is characterized by having set values for use.

  By implementing the present invention, when it is necessary to restart the combustion of the main burner without delay, such as when the steam pressure value suddenly decreases, the combustion of the main burner can be restarted immediately, and the combustion start The followability can be kept high. When a delay is allowed in the combustion restart of the main burner, the fuel consumption and the heat radiation amount due to the pilot combustion can be reduced by not performing the pilot combustion for standby. Further, when the steam load is small, the combustion of the pilot burner is stopped together with the combustion stop of the main burner, so that overshoot at the time of fire transfer can be reduced.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of a boiler embodying the present invention, and FIGS. 2 to 4 are time charts in an embodiment of the present invention. A combustion device 2 for generating a flame downward is provided at the upper center of the boiler, and the flame is burned in the combustion chamber 3 at the center of the boiler. The combustion device 2 is provided with a main burner 5 and a pilot burner 6, and combustion air used in the combustion device 2 is supplied by a blower 10. Combustion air from the blower 10 is sent through the blower passage 7, and the combustion air is rectified in the wind box 8 and supplied to the main burner 5 and the pilot burner 6.

  Fuel is supplied to the combustion device 2 through the fuel supply pipe 4. The fuel supply pipe 4 branches off in the middle and is connected to each of the main burner 5 and the pilot burner 6. The fuel supply pipe 4 connected to the main burner 5 is provided with a main fuel cutoff valve 13, and the fuel supply pipe 4 connected to the pilot burner 6 is provided with a pilot fuel cutoff valve 12. The fuel supply to the main burner 5 is performed by opening the main fuel cutoff valve 13, and the fuel supply to the pilot burner 6 is performed by opening the pilot fuel cutoff valve 12.

  The boiler supplies water from the lower water supply pipe, takes out the steam from the upper steam pipe 9 and sends it to the steam-using device, and provides a pressure detection device 1 for detecting the steam pressure value in the steam section. An operation control device 11 connected to each of the pressure detection device 1, the blower 10, the pilot fuel cutoff valve 12, and the main fuel cutoff valve 13 is provided, and the operation control device 11 controls the operation of each device to operate the boiler. To control.

  The operation control device 11 determines the combustion state of the combustion device 2 in correspondence with the steam pressure value detected by the pressure detection device 1. When the steam pressure value becomes lower than the main combustion start set value, the main combustion is started by the main burner 5, and when the steam pressure value becomes higher than the main combustion stop set value, the combustion in the main burner 5 is stopped. Keep it.

  The operation control device 11 is also set for pilot combustion by the pilot burner 6. The pilot burner 6 serves as a fire type for the main burner 5. The pilot burner 6 burns before the main burner 5 starts to burn, and when the main burner 5 starts burning, the pilot burner 6 stops burning. Further, when the main combustion is shifted to the pilot combustion, the alternate combustion for starting the combustion by the pilot burner 6 is performed immediately before the combustion of the main burner 5 is stopped. A pressure slightly lower than the main combustion stop set value is set as the combustion transition set value, and when the fuel combustion rises to the combustion transition set value due to the main combustion, fuel supply to the pilot burner 6 is started.

  In addition, the operation control device 11 has set a pilot stop determination set value, a pilot stop determination set value, and a time as a set value for detecting the change speed of the steam pressure value as a value that determines the steam pressure value. The pilot stop determination time and pilot stop determination time are set as values. The pilot stop determination time and the pilot stop determination time are values between the main combustion stop set value and the main combustion start set value, respectively. In the embodiment, the pilot stop determination set value and the pilot stop determination set value are set to the same pressure value as the combustion transition set value. Although it is possible to set other values, the configuration of the pressure detecting means can be simplified by setting the same value. In the embodiment, since the pilot stop determination set value and the pilot stop determination set value are set to the same pressure value as the combustion transition set value, the following pilot stop determination set value and pilot stop determination set value are the combustion transition set values. Is written.

  The pilot stop determination time is for determining the stop of the pilot combustion performed after the transition from the main combustion to the pilot combustion, and the time during which the steam pressure value decreases from the main combustion stop set value to the combustion transition set value. Set based on. The pilot stop determination time is for determining whether or not to shift to the pilot combustion when the main combustion is finished, and is a time for the steam pressure value to rise from the combustion shift set value to the main combustion stop set value. Set based on

  Based on the time chart of FIG. 2, the state of operation control will be described. FIG. 2 shows the case where the pilot combustion needs to be continued because the steam pressure value decreases in a short time when the main combustion is stopped. In the case of FIG. 2, first, the steam pressure value rises relatively slowly due to the main combustion by the combustion of the main burner 5. When the steam pressure value reaches the combustion transition set value at the point A and the information that the steam pressure value has increased to the combustion transition set value is sent from the pressure detection device 1 to the operation control device 11, the operation control device 11 Then, the pilot fuel cutoff valve 12 is opened and fuel supply to the pilot burner 6 is started.

  When fuel is supplied to the pilot burner 6, the flame of the main burner 5 spreads to the pilot burner 6, and combustion starts in the pilot burner 6, so that combustion is performed in both the main burner 5 and the pilot burner 6 after point A. It will be. When combustion by the pilot burner 6 is started, the elapsed time from the start of combustion of the pilot burner is measured as an actual measurement time a. The actual measurement time a is the time from the point A where combustion of the pilot burner 6 starts to the point B where the steam pressure value reaches the main combustion stop set value, and the actual measurement time a shown in FIG. It is longer than the stop judgment time. An increase in the actual measurement time a indicates that the increase in the steam pressure value is gradual. Since the change in the steam pressure value is due to the difference between the steam supply amount and the steam usage amount, it can be determined that the steam usage amount is relatively large when the increase in the steam pressure value is moderate. In this case, when the main combustion is stopped and the supply of steam is stopped, it can be expected that the steam pressure value rapidly decreases. If the steam pressure value suddenly decreases, if the preparatory process such as pre-purge is started after the steam pressure value reaches the main combustion start set value, the steam pressure value greatly decreases during the preparatory process. . Therefore, the combustion of the pilot burner 6 is continued so that the combustion of the main burner 5 can be started as soon as the steam pressure value decreases to the main combustion start set value.

  When the steam pressure value becomes the main combustion stop set value at the point B, the operation control device 11 closes the main fuel cutoff valve 13 to stop the fuel supply to the main burner 5 and stop the main combustion. At this time, the combustion by the pilot burner 6 is performed, and the combustion by the pilot burner continues even after the main combustion is stopped, so that at point B, the main combustion is switched to the pilot combustion. Even if the combustion of the main burner 5 is stopped, the steam pressure value is higher than the main combustion stop set value because steam is supplied due to residual heat immediately after the stop. In the case of FIG. 2, pilot combustion is performed after point B, and pilot combustion is an element that increases the amount of overshoot. However, since the amount of steam used is large and the steam pressure value rises slowly, The amount of shoot is small. The pilot combustion has a smaller combustion amount than the main combustion, and the steam supply amount decreases, so that the steam pressure value thereafter decreases.

  In the operation control apparatus 11, the elapsed time from the point B is also measured as the actual measurement time b. The actual measurement time b is the time from the point B where the combustion of the main burner 5 is stopped and the pilot combustion is performed to the point C where the steam pressure value reaches the combustion transition set value, and the actual measurement time b in FIG. It is shorter than the pilot stop judgment time. The fact that the actual measurement time b is short indicates that the steam pressure value is suddenly decreasing. The steam supply amount is determined from the combustion amount, and the change in the steam pressure value is due to the difference between the steam supply amount and the steam usage amount. can do. In this case, if the preparatory process such as pre-purge is started after the steam pressure value reaches the main combustion start set value, the steam pressure value greatly decreases during the preparatory process. By continuing, the combustion of the main burner 5 can be started as soon as the steam pressure value drops to the main combustion start set value.

  When the steam pressure value decreases to the main combustion start set value at the point D, the operation control device 11 immediately opens the main fuel shut-off valve 13 to start fuel supply to the main burner 5 and starts main combustion by the main burner 5. . When combustion by the main burner 5 is started, combustion by the pilot burner 6 becomes unnecessary, so the operation control device 11 closes the pilot fuel cutoff valve 12 and stops combustion of the pilot burner 6.

  In FIG. 2, the pilot combustion is continued, but since the steam pressure is rapidly lowered, the pilot combustion does not take a long time. Further, since the main combustion starts as soon as the steam pressure value decreases to the main combustion start set value, the amount of steam does not become insufficient.

  Next, the state of operation control will be described based on the time chart of FIG. FIG. 3 shows a case where fuel consumption is prevented by not performing pilot combustion while main combustion is stopped because the amount of steam used is small. In the case of FIG. 3, the steam pressure value rises relatively abruptly due to the main combustion by the combustion of the main burner 5. When the steam pressure value reaches the combustion transition set value at the point E and information that the steam pressure value has increased to the combustion transition set value is sent from the pressure detection device 1 to the operation control device 11, the case of FIG. Similarly to the above, the operation control device 11 starts the fuel supply to the pilot burner 6 by opening the pilot fuel cutoff valve 12.

  When combustion by the pilot burner 6 is started, the elapsed time from the start of combustion is measured as an actual measurement time a. The actual measurement time a in FIG. 2 is longer than the pilot stop determination time, which is the set time, but the actual measurement time a in FIG. 3 is shorter than the pilot stop determination time. The fact that the actual measurement time “a” is short indicates that the steam pressure value increases rapidly, and the change in the steam pressure value is due to the difference between the steam supply amount and the steam usage amount. It can be judged that there are few. If the amount of steam used is small, the steam pressure value will not drop suddenly even if the main combustion is stopped, so the amount of steam is not affected even if preparation for combustion is started when the steam pressure value drops to the main combustion start set value. There is no shortage. Therefore, here, when it is determined that the amount of steam is small at point F, the fuel supply to the pilot burner 6 is stopped and the combustion of the pilot burner 6 is stopped. By stopping the pilot combustion for performing the combustion of the pilot burner 6, it is possible to prevent the fuel from being wasted. When the combustion is stopped, it is not necessary to supply combustion air, so the blower 10 also stops operating. If the supply of combustion air is stopped, heat dissipation from the boiler can be reduced.

  Further, when the steam pressure rises suddenly, the amount of overshoot of the steam pressure value after the main combustion stop increases. If the combustion of the pilot burner is continued in this state, the amount of evaporation by the pilot burner 6 is also added, so the increase in the steam pressure value due to overshoot becomes very large. However, in the case of FIG. 3 in which the steam pressure value has risen suddenly, the main combustion is stopped and the combustion of the pilot burner is also stopped, so that the overshoot can be prevented from expanding.

  In FIG. 3, since the pilot combustion is stopped, when the steam pressure value is reduced to the main combustion start set value at the point G, a combustion preparation process such as pre-purge is started. The main combustion can be started after the combustion preparation process is completed and the pilot burner is ignited. During this period, the steam pressure value continues to decrease. However, since the steam pressure value decreases slowly at a time when the amount of steam used is small, the steam pressure value does not decrease as the steam becomes insufficient. Thereafter, when the main combustion is started, the steam pressure value increases.

  Next, the state of operation control will be described based on the time chart of FIG. FIG. 4 shows the case where the main combustion is shifted to the pilot combustion and the pilot combustion is performed, but the pilot combustion is stopped in the middle due to the small amount of steam used. In the case of FIG. 4, the process up to the point H is the same as in FIG. 2, and the pilot combustion is continued even after the main combustion is stopped. Since the pilot combustion has a smaller combustion amount than the main combustion, the steam supply amount decreases, but the steam supply continues. At this time, if the amount of steam used is less than the amount of steam supplied, the steam pressure will increase. Therefore, in FIG. 4, the steam pressure continues to increase even during pilot combustion.

  In the case of FIG. 4 as well, as in FIG. 2, the elapsed time from the start of pilot combustion is measured as the actual measurement time b. The actual measurement time b is the time from the point H at which the combustion of the main burner 5 is stopped to the point J at which the steam pressure value reaches the combustion transition set value. Even when the stop determination time has elapsed, the steam pressure value is not the combustion transition set value. In this case, the operation control device 11 closes the pilot fuel shut-off valve 12 and stops the combustion of the pilot burner 6 at the point I when the pilot stop determination time has elapsed.

  Since the pilot stop determination time is determined based on the time during which the steam pressure value changes from the main combustion stop set value to the combustion transition set value, the main combustion start set value is set from the main combustion stop set value shown in FIG. The time is shorter than the duration T determined based on the time to change to the value. If the steam pressure rises due to pilot combustion, if the pilot combustion stoppage is delayed, an abnormal rise in steam pressure will cause problems such as steam spouting out of the safety valve, but the decision to stop pilot combustion can be made quickly. Therefore, it is possible to prevent the steam pressure from rising abnormally. Also, during pilot combustion, if the steam pressure value decreases but the decrease is gradual, pilot combustion is not necessary, and stopping pilot combustion at an early stage can reduce fuel consumption by pilot combustion. it can.

Outline diagram of boiler implementing the present invention Time chart of an embodiment of the present invention Time chart of an embodiment of the present invention Time chart of an embodiment of the present invention Time chart of the embodiment of the prior art

Explanation of symbols

1 Pressure detection device 2 Combustion device
DESCRIPTION OF SYMBOLS 3 Combustion chamber 4 Fuel supply piping 5 Main burner 6 Pilot burner 7 Air supply path 8 Wind box 9 Steam piping 10 Blower 11 Operation control apparatus 12 Pilot fuel cutoff valve 13 Main fuel cutoff valve

Claims (3)

Based on the pressure or temperature in the boiler, the main combustion by the main burner is stopped when it rises to the main combustion stop set value, and the main combustion is started when it falls to the main combustion start set value. A combustion apparatus for a boiler that enables control to perform pilot combustion by a burner, and a set value for determining a pilot stop that is a value between a main combustion stop set value and a main combustion start set value, and a main combustion stop set value To set the pilot stop determination time determined based on the time required to change from the pilot stop determination set value to
The actual measurement time b is measured from when the main combustion is stopped by reaching the main combustion stop set value until the pressure or temperature decreases to the pilot stop determination set value, and the measured actual time b is set in advance. If it was less than the pilot stop determination time, the pilot combustion was continued and the pilot stop determination set value was not reached even after the set pilot stop determination time had elapsed. In this case, a combustion apparatus for performing pilot combustion control, characterized in that control for stopping pilot combustion in progress is performed. Based on the pressure or temperature in the boiler, the main combustion by the main burner is stopped when it rises to the main combustion stop set value, and the main combustion is started when it falls to the main combustion start set value. A combustion apparatus for a boiler that enables control to perform pilot combustion by a burner, which is a value between a main combustion stop set value and a main combustion start set value, and a pilot stop determination set value and a pilot stop determination setting Set the pilot stop determination time determined based on the time required to change from the value to the main combustion stop set value,
The actual measurement time a from when the pilot combustion determination set value is reached during the main combustion until the pressure or temperature rises to the main combustion stop set value is measured, and the measured actual time a is set in advance. If it is less than the pilot stop determination time, the pilot combustion is stopped, and if the main combustion stop set value is not reached even after the set pilot stop determination time has elapsed, A combustion apparatus for performing pilot combustion control, wherein control for performing combustion is performed. The combustion apparatus for performing pilot combustion control according to claim 2, wherein when the main combustion is started, the combustion of the pilot burner is stopped, and when the main combustion is shifted to the pilot combustion, the main combustion stop setting value and the main combustion start setting are set. When the combustion transition set value, which is a value between the two values, is reached, control is performed to start combustion by the pilot burner by overlapping with the main combustion, and the combustion transition set value is set as the pilot stop determination setting value. A combustion apparatus that performs pilot combustion control.

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